1. Field of the Invention
The present invention relates to a tetrahydroimidazo[1,5-d][1,4]oxazepine derivative having an antagonistic action against group II metabotropic glutamate receptor or a pharmaceutically acceptable acid addition salt thereof. The present invention also relates to a pharmaceutical composition comprising the compound as an active ingredient.
2. Related Background Art
Glutamic acid is known as one of principal excitatory neurotransmitters working for adjusting advanced functions of memory, learning and the like in a central nervous system of a mammal. Glutamate receptors are roughly classified into two types, that is, ionotropic glutamate receptors (iGlu receptors) and metabotropic glutamate receptors (mGlu receptors) coupled with G protein (see Non Patent Document 1).
The iGlu receptors are classified, on the basis of types of their agonists, into three types, that is, N-methyl-D-aspartate (NMDA) receptors, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and kainate receptors. On the other hand, the mGlu receptors have 8 subtypes (mGluR1 to 8) and are classified, on the basis of a signaling system to be conjugated and pharmacological characteristics, into group I (mGluR1, mGluR5), group II (mGluR2, mGluR3) and group III (mGluR4, mGluR6, mGluR7 and mGluR8). The group II and group III mGluRs are expressed as an autoreceptor or a heteroreceptor mainly at the nerve terminal, so as to suppress adenylate cyclase via Gi protein and regulate a specific K+ or Ca2+ channel activity (see Non Patent Document 2).
Antagonists against group II mGluRs, among these glutamate receptors, show an action to improve the cognitive function in animal models and also show an antidepressant action and an antianxiety action, and therefore, it is suggested that group II mGluR antagonists are effective as a novel cognitive function enhancer or antidepressant (see Non Patent Documents 3, 4 and 5).